Inflammatory bower disease (IBD) is a chronic and intractable inflammatory disease of the intestine, and is principally classified into ulcerative colitis and Crohn's disease. In Japan, the number of patients with IBD in 2003 (the number of certified patients, because IBD is designated to be an intractable disease) is approximately 80 thousands patients with ulcerative colitis and approximately 20 thousands patients with Crohn's disease. However, the number of patients is steadily increasing due to Westernized dietary habit; the number of patients in 2003 is 20 times that in 1980 (the number of patients was approximately 5 thousands). In the future, it is expected that the number of young patients increases as well due to further Westernized dietary habit, and there is no doubt about a further increase in the number of patients.
It is indicated that IBD is caused by genetic predisposition, high fat and high protein diet, abnormality in the immune system, and intestinal bacteria, etc., but risk factors of the onset of IBD have not yet been clarified. However, abnormality in the immune system is considered to play an important role in the disease onset.
There is no established therapeutic method for IBD, and diet and rest are applied as general therapy, and steroids and immunosuppressive agents are administered as drug therapy; in addition, antibacterial agents such as Sarazopirin and mesalazine as well as antibiotics may have effects in some cases. Based on these, involvement of intestinal bacteria is indicated, but to date there has been no convincing evidence that a specific intestinal bacterium leads to the onset of disease symptoms.
In recent years, an oral bacterium as a major pathogenic bacterium of caries, i.e., Streptococcus mutans (S. mutans) as a kind of Mutans streptococci, is known to be a causative organism of bacteremia and infective endocarditis. In addition, since bacterial DNA of S. mutans was detected from specimens of heart valve and aortic aneurysm, its association with circulatory diseases has been reported (Non-patent Literature 1). However, there has been no report on the involvement of oral bacteria in inflammation of the digestive tract such as inflammatory bowel disease.